Who Invented Facial Expression Charts?

The Facial Action Coding System was developed by Ekman and Friesen in 1978, according to a report published by the National Institutes of Health. This coding system was an early attempt to develop an observational system to determine the level of pain felt by patients.

Using the facial Action Coding System method for measuring pain can be problematic because it requires extensive training and is based on the subjective judgements of observers, explains the report by Kenneth M Prkachin, PhD RPsych, titled "Assessing Pain by Facial Expression: Facial Expression as Nexus." Subsequent developments have focused on automated analysis, in which the practitioner records a patient's facial expressions and uses information technology to analyze them and look for known pain markers.